OP0151 PREDICTION OF RADIOGRAPHIC PROGRESSION IN PATIENTS WITH ANKYLOSING SPONDYLITIS: USING GROUP-BASED TRAJECTORY MODELING AND DECISION TREE ANALYSIS
Authors: J. Kang, T. H. Lee, B. S. Koo, S. Y. Park, S. Lee, T. H. Kim
Journal: Annals of the Rheumatic Diseases (2022)

Background Ankylosing spondylitis (AS) tends to develop at a relatively young age and is characterized by long-term disease progression (1). During that time, various radiographic changes occur in the spine, which eventually lead to disability in the patient’s lifetime (2). Although the duration of the disease, aging, and passage of time are predicted to be highly associated with spinal progression of AS, it is difficult to predict its progression in the spine of patients. Objectives We aimed to find ways to predict spinal progression over time in patients with AS and analyze its associated clinical factors. Methods Data from the medical records from a single center were extracted between 2001 and 2018. We analyzed the data on patients who fulfilled the modified New York Criteria for AS and had two or more sets of radiographs taken during the observation period. The modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) was estimated by two independent radiologists. Group-based trajectory modeling (GBTM) was used to classify patients into distinct subgroups of longitudinal mSASSS. And when these trajectories and statistically associated factors acted on a patient, which group the patient was most likely to belong to was predicted using a decision tree analysis. Results Data on 1,125 patients were analyzed, and the trajectories were evaluated by dividing them into three groups based on duration of the disease. We confirmed that sex, age at diagnosis, ocular involvement and peripheral joint involvement were associated with the classified spinal progression trajectories. AS onset in older age and ocular involvement were associated with worse radiographic progression, while female sex and peripheral joint involvement were associated with slower radiographic progression (Figure 1 and Table 1). Table 1. Multivariate logistic regression analysis for predictors of mSASSS progression according to disease duration (class 2 and other classes) Variables Univariate Multivariable OR OR 95% CI p -value OR OR 95% CI p -value Lower Upper Lower Upper Sex 2.02 1.39 2.94 &lt;0.001 2.41 1.38 4.21 0.002 Age at diagnosis (10y) 0.50 0.43 0.58 &lt;0.001 0.51 0.42 0.61 &lt;0.001 Ocular involvement 0.61 0.47 0.80 &lt;0.001 0.61 0.44 0.84 0.003 Peripheral involvement 2.14 1.65 2.79 &lt;0.001 2.56 1.86 3.52 &lt;0.001 HLA B27 positivity 0.61 0.32 1.16 0.133 Smoking* &lt;0.001 0.444 Ex-smoker 0.48 0.34 0.62 &lt;0.001 0.78 0.52 1.16 0.218 Smoker 0.56 0.41 0.73 &lt;0.001 0.84 0.57 1.23 0.364 Baseline BASDAI 1.00 0.92 1.09 0.950 Baseline ESR 1.00 1.00 1.00 0.013 Log baseline ESR 0.77 0.70 0.85 &lt;0.001 0.78 0.69 0.88 &lt;0.001 Baseline CRP 0.98 0.94 1.03 0.476 Log baseline CRP 0.78 0.66 0.91 0.002 ¶ ¶ ¶ ¶ Note: Bold text means statistically significant values. *Analysis with non-smoker as a reference. ¶It was excluded when performing multivariate analysis due to multicollinearity. Figure 1. Longitudinal mSASSS trajectory groups for disease duration (A) and decision tree for three trajectory classes (B). (A) Time in month is shown along the x-axis, and logarithmic transformed total mSASSS is shown along the y-axis. The solid line represents the estimated mean in the same-colored area representing the 95% confidence interval. (B) In each terminal node, the class written in bold text is the class representing that node. Conclusion We identified three patterns of radiographic progression according to duration of the disease. The progression trend of patients with AS identified in this study is expected to be helpful in the treatment and management of patients in actual clinical settings. References [1]Braun A, Saracbasi E, Grifka J, Schnitker J, Braun J. Identifying patients with axial spondyloarthritis in primary care: how useful are items indicative of inflammatory back pain? Ann Rheum Dis. 2011;70(10):1782-7. [2]Poddubnyy D, Listing J, Haibel H, Knuppel S, Rudwaleit M, Sieper J. Functional relevance of radiographic spinal progression in axial spondyloarthritis: results from the GErman SPondyloarthritis Inception Cohort. Rheumatology (Oxford). 2018;57(4):703-11. Disclosure of Interests None declared